Barcodes are essential to modern commerce. Virtually any commercially available item receives a barcode identification. Consumers, manufacturers, and retailers all benefit from their use because it is the least expensive yet most reliable way of providing machine-readable information. Given how pervasive barcoding has become for modern commerce, various “barcode verification” schemes have been developed to characterize the quality of a given barcode label. For example, with regard to one-dimensional barcodes, the Uniform Code Council (UCC) has promulgated nine separate categories of barcode quality. To ascertain the quality in these categories, a barcode verifier scans a laser beam across a barcode.
In a conventional barcode verifier, the laser beam is focused into a generally circular illumination spot on the barcode. This illumination spot scans across a “slice” of the barcode during the verification in a direction generally normal to the longitudinal axis of the bars in the barcode. As the illumination spot is scanned, it will cross the unprinted media between the bars. This is problematic because the coherent nature of the laser beam makes it susceptible to specular reflections from the unprinted media. In other words, a given slice of unprinted media between barcode bars may have a spot that strongly reflects the laser light as compared to other unprinted slices of the media. In turn, this specular reflection makes the measurement of contrast between the unprinted media and the bars noisy and unreliable because the increased reflectance diminishes the contrast for the barcode bars on either side of the shiny unprinted media slice. These barcode bars may be printed with acceptable quality yet be deemed unacceptable due to the specular return from the unprinted media.
Accordingly, there is a need in the art for improved barcode verifiers that are less susceptible to specular reflection noise but also retain a small effective aperture size.